嵌套TRY / FINALLY语句的最佳做法 [英] Best practice to do nested TRY / FINALLY statement

问题描述

什么是最好的方式做嵌套的try&最后在delphi中陈述？

Hi What is the best way to do nested try & finally statements in delphi?

var cds1  : TClientDataSet;
    cds2  : TClientDataSet;
    cds3  : TClientDataSet;
    cds4  : TClientDataSet;
begin
  cds1      := TClientDataSet.Create(application );
  try
    cds2      := TClientDataSet.Create(application );
    try
      cds3      := TClientDataSet.Create(application );
      try
        cds4      := TClientDataSet.Create(application );
        try
        ///////////////////////////////////////////////////////////////////////
        ///      DO WHAT NEEDS TO BE DONE
        ///////////////////////////////////////////////////////////////////////
        finally
          cds4.free;
        end;

      finally
        cds3.free;
      end;
    finally
      cds2.free;
    end;
  finally
    cds1.free;
  end;
end;

你能建议一个更好的方法吗？

Can you Suggest a better way of doing this?

推荐答案

如下：

var cds1  : TClientDataSet;
    cds2  : TClientDataSet;
    cds3  : TClientDataSet;
    cds4  : TClientDataSet;
begin
  cds1      := Nil;
  cds2      := Nil;
  cds3      := Nil;
  cds4      := Nil;
  try
    cds1      := TClientDataSet.Create(nil);
    cds2      := TClientDataSet.Create(nil);
    cds3      := TClientDataSet.Create(nil);
    cds4      := TClientDataSet.Create(nil);
    ///////////////////////////////////////////////////////////////////////
    ///      DO WHAT NEEDS TO BE DONE
    ///////////////////////////////////////////////////////////////////////
  finally
    freeandnil(cds4);
    freeandnil(cds3);
    freeandnil(cds2);
    freeandnil(Cds1);
  end;
end;

这使它保持紧凑，只能尝试释放创建的实例。真的没有必要执行嵌套，因为任何失败将导致最终丢弃并执行所提供的示例中的所有清理。

This keeps it compact, and only attempts to free the instances which were created. There really is no need to perform the nesting since ANY failure will result in dropping to the finally and performing all of the cleanup in the example you provided.

我个人不试嵌套在相同的方法...除了try / try / except / finally方案之外。如果我发现自己需要嵌套，那么对我来说，这是一个很好的时间，想想重构到另一种方法调用。

Personally I try not to nest within the same method... with the exception being a try/try/except/finally scenario. If I find myself needing to nest, then to me that is a great time to think refactoring into another method call.

编辑感谢 mghie 和 utku 。

编辑将对象创建更改为不引用应用程序，因为在此示例中它不是必需的。

EDIT changed the object creation to not reference application, as its not necessary in this example.

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